How Do You Convert Frequency Response Function H(iw) to Time Domain h(t)?

Your Name]In summary, the conversation discusses finding the frequency response function by using the input and output spectra. The user has derived the expression for H(iw) and is now trying to convert it to h(t) using the inverse Fourier transform. The steps for finding h(t) have been outlined, and a simplified expression for h(t) has been provided. The user is asked to refer to these steps for converting H(iw) to h(t) and is wished luck with their work.
  • #1
magnifik
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0
I am trying to find the frequency response function given the input and output spectra
11t698h.png


from the picture i got that X(iw) = iU(w)U(2-w) - iU(w+2)U(w) and that
Y(iw) = iwU(w)U(1-w) - iwU(w+1)U(w)

So H(iw) = Y(iw)/X(iw)
and H(iw) = wU(1-w) - wU(w+1) / U(2-w) - U(w+2)

i am having trouble now converting H(iw) to h(t) as i have never divided unit step functions before. can someone tell me if my work above is correct and if so, how to go about finding h(t)? thanks.
 
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  • #2





Your work appears to be correct so far. To convert H(iw) to h(t), you can use the inverse Fourier transform. This will give you the time domain representation of the frequency response function. The steps to do this are as follows:

1. Rewrite H(iw) in the form of a Fourier transform pair, where H(iw) is the transform of h(t). In this case, H(iw) = wU(1-w) - wU(w+1) / U(2-w) - U(w+2) can be rewritten as H(iw) = wU(1-w) - wU(w+1) / (2/pi) * [delta(w-2) + delta(w+2)].

2. Take the inverse Fourier transform of H(iw) to get h(t). This can be done by using the properties of the delta function and the Fourier transform. The result will be h(t) = 1/2 * [tU(t) - (t-2)U(t-2) - (t+2)U(t+2)].

3. Simplify the expression for h(t) to get the final form of the frequency response function. In this case, h(t) can be simplified to h(t) = 1/2 * [tU(t) - tU(t-2) - tU(t+2) + 2U(t+2)].

I hope this helps. Let me know if you have any further questions. Good luck with your work!


 

What is a Frequency Response Function?

A Frequency Response Function (FRF) is a mathematical representation of the relationship between the input and output of a system at different frequencies. It is commonly used in engineering and physics to analyze the behavior of a system in response to different frequencies of input signals.

How is a Frequency Response Function measured?

A Frequency Response Function is typically measured by applying a known input signal to a system and measuring the resulting output at various frequencies. This can be done using specialized equipment such as an oscilloscope or spectrum analyzer.

What factors can affect the shape of a Frequency Response Function?

The shape of a Frequency Response Function can be affected by a variety of factors, including the physical properties of the system (such as mass and stiffness), external forces acting on the system, and the type of input signal being applied.

How is a Frequency Response Function used in practical applications?

Frequency Response Functions are commonly used in practical applications to analyze and improve the performance of systems. They can help identify potential issues, such as resonances or other frequency-dependent behaviors, and guide the design of systems to achieve desired performance.

What are some limitations of using Frequency Response Functions?

While Frequency Response Functions can provide valuable insights into the behavior of systems, they also have some limitations. These include assumptions made in the mathematical models used to calculate FRFs, variations in measurements due to noise or environmental factors, and the need for specialized equipment and expertise to measure and interpret FRFs accurately.

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